Tuberculosis (which includes infection caused by M. tuberculosis, M. bovis, BCG and M. africanum) remains the largest cause of human death in the world from a single infectious disease, and is responsible for one in four voidable adult deaths in developing countries. In addition, in 1990, there was a 10% increase in the incidence of tuberculosis in the United States.
In the past, infection with drug-sensitive strains of the M. tuberculosis complex had been cured with certain antibiotics, including isoniazid, rifampicin, ethionamide and pyrazinamide. However, resistance to isoniazid and other antibiotic drugs has developed in many strains of M. tuberculosis. This has resulted in the search for an effective vaccine against M. tuberculosis. Further, this has enhanced the need to develop new drugs which are effective against drug-resistant strains of M. tuberculosis. It is therefore desirable to develop molecular and genetic tools which can be utilized to understand the pathways involved in invasion, survival and persistance of M. tuberculosis and in the development of vaccines and new drugs.
The creation of mutants in M. tuberculosis and BCG is of essential importance in the analysis of M. tuberculosis and BCG gene function. Auxotrophic mutants have been isolated in M. smegmatis by both shuttle mutagenesis and N-methylN'-nitroso-N-nitrosoguanidine treatment followed by isoniazid enrichment. These methods, however, are less effective in the M. tuberculosis complex (M. tuberculosis, M. bovis, M. miroti and M. africanum) due to current difficulties in performing homologous recombination, which is required by the shuttle mutagenesis procedure. Also, the tendency of mycobacteria to clump limits the use of traditional mutagens and makes positive selection advantageous.
Because the creation of mutants in M. tuberculosis and BCG is of essential importance in the analysis of gene function, it is desirable to develop effective means and methods for delivering foreign DNA into M. tuberculosis and BCG. The insertion of foreign DNA into M. tuberculosis and BCG mycobacteria would provide the necessary tools for understanding the mechanisms by which these mycobacteria survive and replicate. In addition, it would provide valuable tools for the development of vaccines and new drugs effective in the treatment of infection caused by M. tuberculosis and BCG.
It is therefore and object of this invention to provide shuttle phasmids capable of delivering foreign DNA into mycobacteria.
It is another object of this invention to provide a method of producing shuttle phasmids capable of delivering foreign DNA into mycobacteria.
It is a further object of this invention to provide a method of generating mycobacterial mutations.
It is another object of this invention to provide mycobacterial mutants.
It is a still further object of this invention to provide a method of producing a mycobacterial vaccine.